Add "server options" which are server-wide and not bound to a session or

window. Set and displayed with "set -s" and "show -s".

Currently the only option is "quiet" (like command-line -q, allowing it to be
set from .tmux.conf), but others will come along.

key-bindings.c

@@ -224,7 +224,7 @@ key_bindings_info(struct cmd_ctx *ctx, const char *fmt, ...)
 	va_list	ap;
 	char   *msg;
 
-	if (be_quiet)
+	if (options_get_number(&global_options, "quiet"))
 		return;
 
 	va_start(ap, fmt);